molecularity: meaning, definition, pronunciation and examples
C2Technical/Scientific
Quick answer
What does “molecularity” mean?
The number of molecules that participate as reactants in an elementary chemical reaction.
Audio
Pronunciation
Definition
Meaning and Definition
The number of molecules that participate as reactants in an elementary chemical reaction.
In chemistry, a term describing the molecular mechanism of a reaction step; more broadly, can refer to the molecular nature or composition of a substance.
Dialectal Variation
British vs American Usage
Differences
No significant differences in meaning or usage between British and American English. Spelling follows the standard -ity suffix in both.
Connotations
Purely technical/scientific in both varieties.
Frequency
Extremely low frequency in general language; used only within specific chemistry subfields. No regional frequency variation.
Grammar
How to Use “molecularity” in a Sentence
The molecularity of [reaction/step] is [number].[Reaction/Step] has a molecularity of [number].Determining the molecularity requires...Vocabulary
Collocations
Usage
Meaning in Context
Business
Not used.
Academic
Used in advanced chemistry textbooks, research papers, and lectures on chemical kinetics.
Everyday
Never used.
Technical
Core term in physical chemistry for describing elementary reaction steps.
Vocabulary
Synonyms of “molecularity”
Neutral
Weak
Watch out
Common Mistakes When Using “molecularity”
- Confusing 'molecularity' (for an elementary step) with 'order of reaction' (an experimental measurement for the overall rate law).
- Using it to describe the overall reaction instead of a single mechanistic step.
- Misspelling as 'moleculerity' or 'molecularility'.
FAQ
Frequently Asked Questions
No. Molecularity is a theoretical concept for a single, elementary step (must be a small integer: 1, 2, or 3). Reaction order is an experimentally determined exponent in the rate law and can be fractional, zero, or negative.
Almost never in practice. A molecularity greater than three (termolecular) is statistically very unlikely because it requires three molecules colliding simultaneously with the correct orientation and energy. Most elementary steps are uni- or bimolecular.
It is a core term in chemical kinetics, a sub-discipline of physical chemistry.
No. It is a highly specialized technical term unknown to the general public and rarely encountered outside advanced chemistry contexts.
The number of molecules that participate as reactants in an elementary chemical reaction.
Molecularity is usually technical/scientific in register.
Molecularity: in British English it is pronounced /məˌlɛkjʊˈlærɪti/, and in American English it is pronounced /məˌlɛkjəˈlærəti/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Think: 'MOLECULAR-ity' – it's about counting MOLECULES (how many?) involved in a single reaction step.
Conceptual Metaphor
A TEAM SIZE: Molecularity is like specifying how many players (molecules) must come together to start a play (the reaction step).
Practice
Quiz
What does 'molecularity' specifically describe in chemistry?